Vitamin D (i.e., Vitamin D3) is a fat-soluble vitamin produced from ergosterol and 7-dehydrocholesterol following exposure to sunlight. Vitamin D is also easily obtainable from foods, including Vitamin D enriched foods such as milk, and from vitamin supplements. Another excellent source of Vitamin D for infants, and sometimes the sole source, is infant formulas that have been fortified with Vitamin D.
The benefits of Vitamin D are well documented and accepted. Such benefits include regulation of calcium in the body, and coordination of the deposit of calcium and phosphorous into the bone. Vitamin D and other vitamins are often added to various nutritional products, including infant and adult nutritional formulas. In addition to the Vitamin D and other vitamin supplements in such formulas, these products typically also contain a balance of carbohydrate, lipid, and protein nutrients, the latter of which is most often supplied and consumed in the form of common intact proteins.
Some people, however, exhibit allergies or sensitivities to intact proteins, i.e. whole proteins, such as those in intact cow's milk protein or intact soy protein isolate-based formulas. While such sensitivities are more common in infants than in children over one year of age or adults, there are still some people over the age of one with these sensitivities. Many of these people with protein allergies or sensitivities are able to tolerate extensively hydrolyzed protein. Hydrolysate formulas (also referred to as semi-elemental formulas) contain protein that has been hydrolyzed or broken down into short peptide fragments and amino acids and as a result is more easily digested. In people with protein sensitivities or allergies, immune system associated allergies or sensitivities often result in cutaneous, respiratory or gastrointestinal symptoms such as vomiting and diarrhea. People who exhibit reactions to intact protein formulas often will not react to extensively hydrolyzed protein formulas because their immune system does not recognize the hydrolyzed protein as the intact protein that causes their symptoms.
Nutritional guidelines for infant formulas can be found in the Infant Formula Act, 21 United States Code (U.S.C.) Section 350(a). This Act currently specifies that the maximum allowable amount of Vitamin D in an infant formula is 676 I.U. per liter, and the minimum allowable amount of Vitamin D is 274 I.U. per liter, the range being based upon a standard 20 calorie/ounce formula. (equivalent I.U./liter ranges must be adjusted for other base infant formulas, e.g. 24 calorie/ounce).
To meet the Vitamin D requirements of the Infant Formula Act, the amount of Vitamin D in an infant formula must fall somewhere between the minimum and maximum for the entire shelf-life of the formula. For example, currently available Similac□ with Iron (available from Ross Products Division of Abbott Laboratories, Columbus, Ohio) has a label value of 60 I.U. of Vitamin D per 100 kcal or 148 milliliters of formula, corresponding to approximately 405 I.U. of Vitamin D per liter.
It is generally known, however, that Vitamin D degrades and concentrations decline after packaging and when used in combination with extensively hydrolyzed protein in a liquid nutritional formula. This rapid degradation, which will generally occur throughout the shelf-life of the liquid nutritional formula, creates a challenge for the formulator in providing a finished product with acceptable Vitamin D concentrations over the desired shelf-life of the product. This Vitamin D shelf-life stability problem is described in U.S. Pat. No. 5,456,926 (Hill et al.), which description is incorporated herein by reference.
One method of improving the shelf-life stability of Vitamin D in a liquid nutritional formula is described in U.S. Pat. No. 5,456,926 (Hill et al.) which teaches the addition of Vitamin C to a liquid nutritional formula, before or after a preliminary heat treatment, at a concentration exceeding 300 mg per liter, such that the initial concentration of Vitamin C will be at least 300 mg per liter during the shelf-life of the liquid nutritional product.
Yet another method of addressing the shelf-life stability of Vitamin D in a liquid nutritional formula containing extensively hydrolyzed protein involves over-fortification with Vitamin D during processing, i.e., prior to packaging. In other words, enough Vitamin D is added during formulation to compensate for the anticipated degradation and loss of Vitamin D during the packaged shelf-life of the liquid nutritional product. This method, however, is limiting in that it does not effectively slow down Vitamin D degradation after packaging, and care must therefore be taken during the over-fortification step to avoid excessive Vitamin D concentrations in the initially marketed product.
It has now been found, however, that the shelf-life stability of Vitamin D can be improved even when formulated in the presence of extensively hydrolyzed protein in a liquid nutritional formula, provided that the formula is aseptically packaged in accordance with the methods described hereinafter. It has been found that such aseptic packaging methods when applied to these formulas provide for improved Vitamin D shelf-life stability as compared to other similar formulas packaged in accordance with more conventional retort packaging methods.
Although aseptically packaged liquid nutritional formulations are known in the literature, some of which are also marketed and available to consumers, including infant nutritional formulas, none of these formulations are believed to contain hydrolyzed protein or extensively hydrolyzed protein with a sufficient degree of hydrolysis (i.e., at least about 20%,) that would otherwise greatly accelerate Vitamin D degradation. Non-limiting examples of these prior art formulations include Similac□ with Iron, Isomil□ Soy Formula with Iron, and Ensure7, all of which are available from Ross Products Division of Abbott Laboratories, Columbus, Ohio, U.S.A. (all contain intact protein). Other aseptically packaged formulas include Neocate® One Elemental Liquid Nutrition (contains non-hydrolyzed amino acids) and Good Start Infant Formula, available from Nestle USA, Eau Claire, Wis., U.S.A. (contains hydrolyzed protein but with a degree of hydrolysis less than about 20%). .